Connection Failure Notification Method And Apparatus

ABSTRACT

An access point according to the present invention generates and broadcasts a notification message to the mobile devices serviced by an access point upon detection of a connection failure between the serving access point and a network node. The notification message controls the impact of the connection failure on neighboring cells by including redirect information that identifies one or more alternate access points for the affected mobile devices. The affected mobile devices subsequently attempt to access the access points identified by the redirect information. The notification message may also include timing information that informs the affected mobile devices when they may attempt to access an alternate access point identified by the redirect information.

TECHNICAL FIELD

The present invention relates generally to transmission interfacefailures between network nodes in a wireless communication system.

BACKGROUND

Wireless communication systems typically include multiple wirelessnetworks that rely on different radio access technologies to exchangeinformation between a core network and a mobile device, such as acellular telephone. In general, the mobile device communicates with anaccess point in one of the wireless networks according to the radioaccess technology associated with the wireless network, e.g., GSM, UMTS,LTE, etc. The access point in turn communicates with the core networkaccording to the appropriate radio access technology. Suchcommunications operate without interruption as long as the communicationlink(s) between the mobile device and the core network are maintained. Afailure in one or more of the communication links jeopardizes theongoing communications between the mobile device and the core network.

For example, when operating in a UMTS network, the mobile devicecommunicates with a NodeB access point. The NodeB in turn communicateswith the core network via a Radio Network Controller (RNC). A failure inthe communication link between the NodeB and the RNC, or between the RNCand the core network prevents the NodeB from operating properly.Similarly, when operating in an LTE network, a failure in thecommunication link between the eNodeB access point and the core networkprevents the eNodeB access point from working properly.

When prior art networks encounter this problem, the affected mobiledevices enter an idle mode. During idle mode operation, the mobiledevices may attempt to access a different access point to reestablishcommunications with the core network. In some cases, one or more of themobile devices may attempt to access an access point associated with adifferent radio access technology. Alternatively or additionally, someor all of the mobile devices may attempt to simultaneously access thesame access point in a neighboring cell. These types of transitions mayput an undesirably large strain on the affected neighboring cells.Further, functionality to have optimized neighbor cell relations in anetwork may be based on UE measurements on neighbor cells. A failure inthe communication link between the access point and the core network mayimpact this functionality.

SUMMARY

The present invention addresses connection failures between an accesspoint and a network node, such as the core network, in a wirelesscommunication system. More particularly, a connection processor in anaccess point monitors a connection between the access point and thenetwork node. Upon detection of a connection failure, the connectionprocessor generates and broadcasts a notification message to the mobiledevices serviced by the access point. According to one exemplaryembodiment, the notification message includes redirect information thatidentifies one or more alternate access points for the affected mobiledevices. The redirect information enables the affected access point tocontrol the impact of the connection failure on neighboring cells.Further, the redirect information enables the affected access point todictate the type of access point(s), and therefore the particular radioaccess technology, utilized by the affected mobile devices. The mobiledevices subsequently attempt to access the access points identified bythe redirect information. By providing redirect information with aconnection failure notification message, the present inventionadvantageously provides means for protecting neighbor cells fromoverload, prevents the affected mobile devices from attempting to use adifferent radio access technology, and enables the mobile devices toavoid entering the idle mode.

The notification message may also include timing information thatinforms the affected mobile devices when they may attempt to access analternate access point identified by the redirect information. Forexample, the timing information may provide a specific redirection timefor some or all of the mobile devices. Thus, the timing informationadvantageously controls the redirection of the affected mobile devicesto prevent multiple mobile devices from redirecting at the same time.Alternatively, the timing information may instruct some or all of themobile devices to wait for a second notification message beforeattempting to access an alternate access point. In this case, the secondnotification message may control the redirection time by explicitlyinstructing a mobile device to begin the access attempt. Alternatively,the second notification message may notify a mobile device that theoriginal serving access point has reestablished connection with the corenetwork, and therefore, that no redirection is required. In this case,the second notification message advantageously informs the affectedmobile devices that no redirection is needed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a wireless communication system applicable to the presentinvention.

FIG. 2 shows an exemplary process according to the present invention.

FIG. 3 shows an exemplary block diagram of an access point in thewireless communication system of FIG. 1.

DETAILED DESCRIPTION

FIG. 1 shows one exemplary wireless communication system 10. Thewireless communication system 10 includes one or more access points 40that enable wireless communications with mobile devices 20, such asmobile telephones, personal digital assistants, laptop computers, etc.The access points 40 may implement the same access technology, or mayimplement different access technologies. For a GSM network, the accesspoint 40 comprises a Base Transceiver Station (BTS), while for UMTS andLTE networks, the access point 40 comprises a NodeB and an eNodeB,respectively. While not shown, other access points 40, e.g., a WLANaccess point, may be included in wireless communication system 10. Theaccess points 40 connect the mobile device 20 to a core network 30. Fora GSM network, the BTS 40 connects to a Base Station Controller (BSC) 50over an Abis interface, and the BSC 50 in turn connects to the corenetwork 30. For a UMTS network, the NodeB 40 connects to a Radio NetworkController (RNC) 52 over an lub interface, and the RNC 52 in turnconnects to the core network 30. For an LTE network, the eNodeB connectsto a serving gateway and mobility management entity in the core network30 via an S1 interface.

When the connection between an access point 40 and the core network 30is interrupted or fails, e.g., as shown with the LTE network in FIG. 1,the affected access point 40 is typically removed from service andmobile devices 20 served by the removed access point 40 switch to anidle mode. During idle mode, the mobile devices 20 select and attempt toaccess a new access point 40 as soon as possible to reestablishcommunications with the core network 30.

The mobile devices 20 may select an access point 40 using a differentradio access technology than the originally serving access point 40.Further, the abrupt transition of multiple mobile devices 20 to a newaccess point 40 may undesirably overload neighboring access points 40.

According to embodiments of the present invention, an access point 40monitors the state of its connection to the core network 30 andbroadcasts a notification to the mobile devices 20 when the connectionis interrupted or fails. The access point 40 may also broadcast redirectinformation to the mobile devices 20 to indicate the preferred accesspoints 40 available for reselection by the mobile devices 20. Theredirect information may also indicate specific times when the mobiledevices 20 should switch to the neighboring access points 40. Thus, themobile devices 20 may be “scheduled” so that large numbers of mobiledevices 20 do not all switch to the same neighboring access point 40 atthe same time.

FIG. 2 illustrates an exemplary method 100 implemented by an accesspoint 40. The serving access point 40 monitors the connection betweenthe access point 40 and the core network 30 (block 110). Upon detectionof a connection failure (block 120), the access point 40 generates andbroadcasts a notification to the mobile devices 20 (block 130)indicating that the access point is out-of-service. The broadcastednotification includes redirect information that identifies one or morealternate access points 40 available for reselection by the mobiledevices 20. For example, the redirect information may identify an accesspoint 40 of a neighboring cell. The redirect information may alsoinclude scheduled times for the mobile devices 20 to switch to theneighboring access points 40.

Access points 40 may generate the redirect information of thenotification message based on any available neighboring cellinformation. For example, a serving access point 40 may identifymultiple alternate access points 40 based on the number of mobiledevices 20 currently under the control of the serving access point 40,the current load of neighboring access points 40, etc. It will beappreciated that some or all of the load information required togenerate the redirect information may be provided by the neighboringaccess points 40 via an interface between the access points, e.g., an X2interface, and/or by the mobile devices 20. Regardless, the broadcastednotification message identifies specific alternate access points 40available to the mobile devices 20 affected by the connection failure.

Responsive to the notification message, the mobile devices 20 attempt toaccess one of the alternate access points 40 identified by thebroadcasted notification message to continue communications with thecore network 30. It will be appreciated that the redirect informationmay identify specific alternate access points 40 for specific mobiledevices 20. For example, the redirect information may specify that onemobile device 20 should access a first alternate access point 40, andthat another mobile device 20 should access a second alternate accesspoint 40. Alternatively, each mobile device 20 may select one of theaccess points 40 identified by the redirect information according tosome predetermined criteria. For example, a mobile device 20 may selectone of the identified access points 40 by selecting the closestidentified access point 40. In any event, the redirect informationcontrols which alternate access points 40 are accessed by the mobiledevices 20 in the event of a connection failure at the serving accesspoint 40.

While not required, the broadcasted notification message may includetiming information that controls when some or all of the mobile devices20 may attempt to access an alternate access point 40 identified by theredirect information. For example, the timing information may identify adesignated access time for some or all of the mobile devices 20, whereeach mobile device 20 attempts to access an alternate access point 40 atits designated access time. Alternatively, the timing information mayinstruct some or all of the mobile devices 20 to wait for a secondnotification message before attempting to access an alternate accesspoint 40. In this case, the serving access point 40 may delaytransmission of the second notification message to delay the transitionsof the mobile devices 20 to the alternate access points 40. Thus, thesecond notification message may be used to control when each mobiledevice 20 transitions to an alternate access point 40.

In still another example, where the timing information instructs some orall of the mobile devices 20 to wait for a second notification message,the access point 40 may delay sending the second notification message apredetermined time period while it attempts to reestablish theconnection with the core network 30. If the access point 40 issuccessful, the second notification message may inform some or all ofthe mobile devices 20 that the connection has been reestablished, whicheffectively cancels the first notification message. If the access point40 is not successful within the predetermined time period, the accesspoint 40 may delay transmission of the second notification message todelay the transitions of the mobile devices 20 to the alternate accesspoints 40, and therefore, to control when each mobile device 20transitions to an alternate access point 40.

FIG. 3 shows an exemplary block diagram of an access point 40 accordingto the present invention. The access point includes a transceiver 42 andcontrol logic 44. The transceiver connects to an antenna that wirelesslycommunicates with the mobile devices 20 according to instructionsprovided by the control logic 44. The control logic further includes aconnection processor 46 that implements the above-described process fornotifying a mobile device 20 of a connection failure between the accesspoint 40 and the core network 30.

The above-described invention addresses the issues associated with priorart solutions for connection failures between an access point 40 and acore network 30 in a wireless communication system 10. By directing themobile devices 20 affected by the connection failure to specificalternate access points 40, the present invention controls the impact ofthe connection failure on neighboring cells. Further, the presentinvention may prevent multiple mobile devices 20 from simultaneouslyattempting to access one access point 40 by providing means forcontrolling the timing associated with the transition of the mobiledevices 20 to alternate access points 40. Further still, the presentinvention enables one access point 40 to continue to dynamically keeptrack of other access points 40. For example, in conventional systems,an access point 40 associated with a connection failure may be deletedfrom the neighbor lists of neighboring access points 40 due to a lack ofproposed neighbors from mobile device measurements for an access point40 associated with a connection failure. The present invention allowsthe affected access point 40 to stay on the neighbor lists of theneighboring access points 40 with the understanding that the affectedaccess point 40 is unavailable until the connection is restored. In thiscase, one or more of the affected mobile devices 20 may report theconnection failure to one or more neighboring access points.

The present invention may, of course, be carried out in other specificways than those herein set forth without departing from the scope andessential characteristics of the invention. The present embodiments are,therefore, to be considered in all respects as illustrative and notrestrictive, and all changes coming within the meaning and equivalencyrange of the appended claims are intended to be embraced therein.

1. A method of notifying mobile devices of a connection failure betweenan access point and a network node in a wireless communication system,the method comprising: detecting a connection failure for an interfacebetween the access point and the network node; and generating andbroadcasting a notification message responsive to the connection failureto notify mobile devices serviced by the access point of the connectionfailure, wherein the notification message includes redirect informationthat identifies one or more alternate access points for the mobiledevices.
 2. The method of claim 1 wherein the notification messageincludes timing information identifying when one or more of the mobiledevices should redirect to an alternate access point.
 3. The method ofclaim 2 wherein the timing information comprises redirection times forone or more of the mobile devices.
 4. The method of claim 2 wherein thetiming information instructs one or more of the mobile devices to waitfor second notification message before redirecting to one of thealternate access points.
 5. The method of claim 4 further comprisingtransmitting the second notification message to one or more of themobile devices at different times.
 6. The method of claim 4 furthercomprising: reconfiguring the interface to reestablish the connectionbetween the access point and the network node; and broadcasting thesecond notification message to the mobile devices to notify the mobiledevices of the reestablished connection to overturn the pendingredirection operation.
 7. The method of claim 1 further comprising:reconfiguring the interface to reestablish the connection between theaccess point and the network node; and broadcasting a secondnotification message regarding the reestablished connection.
 8. Anaccess point in a wireless communication system, the access pointcomprising a connection processor configured to: detect a connectionfailure for an interface between the access point and a network node inthe wireless communication system; and generate and broadcast anotification message responsive to the connection failure to notifymobile devices serviced by the access point of the connection failure,wherein the notification message includes redirect information thatidentifies one or more alternate access points for the mobile devices.9. The access point of claim 8 wherein the notification message includestiming information identifying when one or more of the mobile devicesshould redirect to an alternate access point.
 10. The access point ofclaim 9 wherein the timing information comprises redirection times forone or more of the mobile devices.
 11. The access point of claim 9wherein the timing information instructs one or more of the mobiledevices to wait for second notification message before redirecting toone of the alternate access points.
 12. The access point of claim 11wherein the connection processor is further configured to transmit thesecond notification message to one or more of the mobile devices atdifferent times.
 13. The access point of claim 11 wherein the connectionprocessor is further configured to: reconfigure the interface toreestablish the connection between the access point and the networknode; and broadcast the second notification message to the mobiledevices to notify the mobile devices of the reestablished connection tooverturn the pending redirection operation.
 14. The access point ofclaim 8 wherein the connection processor is further configured to:reconfigure the interface to reestablish the connection between theaccess point and the network node; and broadcast a second notificationmessage regarding the reestablished connection.
 15. A method ofnotifying a mobile device of a connection failure between an accesspoint and a network node in a wireless communication system, the methodcomprising: receiving a broadcasted notification message indicating aconnection failure between the access point and the network node,wherein the notification message includes redirect informationidentifying one or more alternate access points for the mobile device;and using the redirect information to access one of the alternate accesspoints.
 16. The method of claim 15 wherein the notification messageincludes timing information identifying when the mobile device shouldredirect to one of the alternate access points.
 17. The method of claim16 wherein using the redirect information to access one of the alternateaccess points comprises using the redirect information to access one ofthe alternate access points at an explicit redirection time identifiedby the timing information.
 18. The method of claim 16 wherein the timinginformation instructs the mobile device to delay accessing one of thealternate access points until a second notification message is received.19. The method of claim 18 wherein the second notification messageinforms the mobile device of a reestablished connection between theaccess point and the network node.
 20. The method of claim 15 furthercomprising reporting the connection failure to one or more alternateaccess points.
 21. A mobile device operatively associated with an accesspoint in a wireless communication system, the mobile device methodcomprising a processor configured to: receive a broadcasted notificationmessage indicating a connection failure between the access point and anetwork node in the wireless communication system, wherein thenotification message includes redirect information identifying one ormore alternate access points for the mobile device; and use the redirectinformation to access one of the alternate access points.
 22. The mobiledevice of claim 21 wherein the notification message includes timinginformation identifying when the mobile device should redirect to one ofthe alternate access points.
 23. The mobile device of claim 22 whereinthe processor use the redirect information to access one of thealternate access points at an explicit redirection time identified bythe timing information.
 24. The mobile device of claim 22 wherein thetiming information instructs the mobile device to delay accessing one ofthe alternate access points until a second notification message isreceived.
 25. The method of claim 24 wherein the second notificationmessage informs the mobile device of a reestablished connection betweenthe access point and the network node.